This invention relates to the gettering of hydrogen and other gases. It further relates to the use of the process in fusion devices.
The art provides numerous methods for gettering or pumping hydrogen gas. One of the techniques often employed for this purpose is to coat a gettering material on the inside surface of a vessel from within which hydrogen is to be removed. Typically, the material is heated to a few hundred degrees to activate its sorbing capacity. Sometimes, the pumping or sorbing capability of the gettering material deteriorates when non-compatible gases are present in the system. Another approach is to incorporate a gettering material in a porous structural material, a polymeric foam for insurance, so that hydrogen capture may occur over a long period of time and prevent damage to an electronic or other type of device that has to be stored for an intermediate period.
Thus, a gettering material formed by coating a Group VIII metal hydrogenation catalyst with certain unsaturated organic materials such as dimerized benzylacetylene (Anderson et al, U.S. Pat. No. 3,963,826) and then using such coated material in a closed volume to getter hydrogen (Anderson et al, U.S. Pat. No. 3,896,042). Catalytic nickel has been used to dissociate hydrocarbons and active zirconium-aluminum alloys employed to sorb the resultant hydrogen while the carbon formed is deposited on the catalyst (Young, U.S. Pat. No. 4,515,528). Supported getters have been disclosed which comprise a three-dimensional titanium or nickel structure defining up to 100 interconnecting free cells per inch which contain particulate zirconium and particulate graphite (Barosi et al, U.S. Pat. No. 4,146,497)
Another system for scavenging organic gases is composed of a dissociator and a scavenging pump (Coppola, U.S. Pat. No. 3,221,197). The dissociator may be pyrolytic, catalytic, or it may be an ionizer. The carbon formed by the decomposition of the organic gases deposits on the walls of the apparatus and serves as a scavenging layer for some of the other dissociation products, e.g., fragments of hydrocarbons, carbon monoxide, carbon dioxide, and the like. Molecular filtration is used to remove most organic gases produced and what remains is exposed to a scavenging pump. When hydrogen is the principal residual gas, a pump consisting of a suitable heated material having good hydrogen absorption capability, such as titanium, is recommended. One disadvantage of the system just described in is the contamination of the ionization source, when such is used in the dissociator, by carbon or organic materials.
Amorphous carbon deposits similar to those already mentioned have also been formed from sputtered carbon. (See Plasma Deposited Thin Films, Chapter 4, CRC Press, Inc., Boca Raton, Fla. 1986.)